Re: [PATCH 06/10] xfs: regularize iclog space accounting in xlog_write_partial

["Darrick J. Wong" <djwong@kernel.org>]

On Thu, Oct 30, 2025 at 03:49:16PM +0100, Christoph Hellwig wrote:
> When xlog_write_partial splits a log region over multiple iclogs, it
> has to include the continuation ophder in the length requested for the
> new iclog.  Currently is simply adds that to the request, which makes
> the accounting of the used space below look slightly different from the
> other users of iclog space that decrement it.  To prepare for more code
> sharing, adding the ophdr size to the len variable before the call to
> xlog_write_get_more_iclog_space and then decrement it later.
> 
> This changes the contents of len when xlog_write_get_more_iclog_space
> returns an error, but as nothing looks at len in that case the
> difference doesn't matter.

Ooops, sorry I missed this patch. :(

It makes sense to me that we have to account for the continuation when
asking for a fresh iclog, but now I have a question.  In "xfs: improve
the calling convention for the xlog_write helpers", the len pointer
becomes xlog_write_data::bytes_left.  In the context of this patch, I
guess that means "len" is the amount of log data that we still have to
write to the log, correct?

--D

> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/xfs_log.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
> index 93e99d1cc037..539b22dff2d1 100644
> --- a/fs/xfs/xfs_log.c
> +++ b/fs/xfs/xfs_log.c
> @@ -2048,10 +2048,10 @@ xlog_write_partial(
>  			 * consumes hasn't been accounted to the lv we are
>  			 * writing.
>  			 */
> +			*len += sizeof(struct xlog_op_header);
>  			error = xlog_write_get_more_iclog_space(ticket,
> -					&iclog, log_offset,
> -					*len + sizeof(struct xlog_op_header),
> -					record_cnt, data_cnt);
> +					&iclog, log_offset, *len, record_cnt,
> +					data_cnt);
>  			if (error)
>  				return error;
>  
> @@ -2064,6 +2064,7 @@ xlog_write_partial(
>  			ticket->t_curr_res -= sizeof(struct xlog_op_header);
>  			*log_offset += sizeof(struct xlog_op_header);
>  			*data_cnt += sizeof(struct xlog_op_header);
> +			*len -= sizeof(struct xlog_op_header);
>  
>  			/*
>  			 * If rlen fits in the iclog, then end the region
> -- 
> 2.47.3
> 
>